[CIR] Upstream Emit the resume branch for cir.await op (#169864)
This PR upstreams the emission of the `cir.await` resume branch.
Handling the case where the return value of `co_await` is not ignored is
deferred to a future PR, which will be added once `co_return` is
upstreamed. Additionally, the `forLValue` variable is always `false` in
the current implementation. When support for emitting `coro_yield` is
added, this variable will be set to `true`, so that work is also
deferred to a future PR.